Botulinum toxin for treatment of dystonia

Botulinum toxin (BT) is used in various medical specialties. However, dystonia is still one of the most important indications for BT therapy. BT drugs consist of botulinum neurotoxin, complexing proteins and excipients. Botox (R), Dysport (R) and Xeomin (R) are BT type A drugs and produce similar therapeutic and adverse effects (AE). Neurobloc (R)/MyoBloc (R) is based upon BT type B. Its use is limited by substantial systemic anticholinergic AE. The potency of BT drugs may be compared as follows: Botox (R):Xeomin (R):Dysport (R):Neuobloc (R)/MyoBloc (R) - 1:1:3:40. BT selectively blocks the cholinergic innervation of striate and smooth muscles and exocrine glands. It can produce obligate, local and systemic AE. However, its overall AE profile including long-term safety is excellent. BT can be blocked by antibodies. Risk factors include single doses, interinjection intervals and the immunological quality of the BT drug applied. Planning of BT therapy is based upon target muscle identification and estimation of their dystonic involvement. For planning of BT therapy and BT placement, electromyography and imaging techniques may be used additionally. So far, total Xeomin (R) and Botox (R) doses of up to 840 MU have been used without clinically detectable systemic AE. BT can be used to treat focal dystonias including cranial, pharyngolaryngeal, cervical and limb dystonias. In segmental and generalized dystonias, BT therapy has to be focussed on the most relevant target muscles. Combinations with all other treatment options including deep brain stimulation are possible. Recent safety data and availability of immunologically improved BT drugs are now allowing higher BT doses thus expanding the use of BT into more widespread dystonias.